Rotary suction drum filter



Oct. 2, 1956 J. STRINDLUND 2,765,085

ROTARY SUCTION DRUM FILTER Filed Feb. 24, 1954 2 Sheets-Sheet 1 FIG -1F! G 3 1o 2 INVENTOR.

JOHN STRINDLUND ATTORNEYS Oct. 2, 1956 J. STRINDLUND ROTARY sucnou DRUMFILTER 2 Sheets-Sheet 2 Filed Feb. 24, '1954 INVENTOR.

JOHN STRINDLUND Mafi ATTORNEYS Patented Oct. 2, 1955 ROTARY SUCTION DRUMFILTER John Strindlund, Upsala, Sweden, assignor to The Black- ClawsonCompany, Hamilton, Ohio, a corporation of Ohio Application February 24,1954, Serial No. 412,335

Claims. (Cl. 210-202) This invention relates to rotary suction drumfilters of the type including a cylindrical strainer disposed in spacedrelation to the outer surface of an inner shell or casing, acircumferential row of longitudinally extending cells located betweenthe casing and the strainer and each having an outlet, and rearwardlybent discharge ducts leading from the outlets of the cells to dischargethe liquid entering the cells through the strainer.

One of the primary objects of the invention is to provide such a rotaryfilter which includes a stationary suction box located in such relationwith the drum that it registers successively with the discharge ends ofthe discharge ducts during a part of the rotational movement of eachduct to increase the effective suction through the corresponding cell.

In accordance with the invention, the suction box is so constructed andarranged with respect to the rotating discharge ducts that the dischargeend of each duct reaches the suction area of the box at a predeterminedinterval when the duct is substantially filled with liquid and itsassociated cell is wholly immersed in the pulp suspension outside thedrum but is still partly filled with air. As the discharge end of theduct passes across the suction area of the suction box, a substantialportion of the liquid is withdrawn from the duct, and this in turncreates a partial vacuum within the duct which promotes further suctionthrough the outer surface of the associated cell.

Further in accordance with the invention, the suction box is arranged toshut oii outward flow from the discharge duct for a substantial intervalfollowing passage of the discharge end of the duct across the suctionarea and thereby to provide time for the additional suction into theassociated cell resulting from the partial vacuum in the cell and duct.Thereafter, the discharge end of the duct is uncovered for free drainageinto a liquid chamber adjacent the suction box. The liquid from thischamber may in turn be pumped to the first washing stage of the pulp onthe exposed surface of the filter, particularly if it is desired toobtain relatively concentrated liquor from the pulp, or'if concentrationof liquor is not important, this drained liquid may be conveyed from thechamber to the downspout of the suction box to augment its suctioneffect.

This construction in accordance with the invention provides a furtheradvantage in that substantially no air reaches the downspout of thesuction box so that a highly effective vacuum can be maintained.therein. At the same time, if foam or gas should be present with theliquid reaching the suction box, the upper part of the box may readilybe connected to a suction pump for removing such foam or gas separatelyfrom the liquid.

It is an object of the present invention to provide a rotary suctiondrum filter having the structural and operational characteristicsoutlined above, and especially to provide such a filter in which thedischargeducts are arranged to discharge at one or both ends of the drumand in which there is a suction box correspondingly located at one orboth ends of the drum for cooperation with the discharge ends of thedischarge ducts.

Additional objects and advantages of the invention will be apparent fromthe following description, the accompanying drawings, and the appendedclaims.

In the drawings- Fig. l is a sectional view taken on the line 1--1 ofFig. 2 and showing a rotary suction drum filter constructed inaccordance with the invention;

Fig. 2 is a radial section on the line 2-2 of Fig. 1;

Figs. 3 and 4 are fragmentary sectional views similar to Fig. 2 andillustrating moved positions of one of the discharge ducts with relationto the suction box;

Fig. 5 is a section on the line 55 of Fig. 6 illustrating anotherconstruction of filter in accordance with the invention;

Fig. 6 is a section on the line 66 of Fig. 5;

Fig. 7 is a developed side elevational view of the filter of Figs. 5 and6 with the strainer removed; and

Fig. 8 is a view similar to Fig. 1 showing a filter in accordance withthe invention having a suction box at each end thereof.

Referring to the drawings, which illustrate preferred embodiments of theinvention, in Figs. 1 and 2, the cylindrical perforate strainer 10 issupported on an inner shell or casing shell or casing shown as formed bytwo drum sections 11 and 12 of the same diameter connected in axiallyspaced relation by a middle drum section 13 of lesser diameter. One endof the drum. is extended beyond the strainer 10 to form a cylindricalsuction face 15, and the drum as a whole is supported by end plates 16and 17 on a shaft 18 for rotation in the vat indicated diagrammaticallyat 19. The annular space between the strainer 10 and the inner casing isseparated into a plurality of cells 29 by generally radially and axiallyextending walls 21, and each cell 26 has an outlet 22 formed by walls 23in the space bounded by the drum section 13 and the adjacent end wallsof the drum sections 11 and 12.

Each of the outlets 22 is provided with a discharge duct 25 formed ofpipe or flexible tubing opening through the end wall of the drum section12 and extending axially of the drum in a generally helical spiral inthe direction opposite the direction of rotation of the drum indicatedby the arrow in Fig. 2 to locate the discharge end of each duct at thedesired angular spacing rearwardly of its associated outlet, referencebeing made in this connection to my copending application Serial No.412,334 filed of cludes an extended contact face 31 adapted to engagethe suction face sufiiciently tightly to close the discharge outlets 26of the ducts as they pass thereacross with the rotating drum. Thesuction box 39 is surrounded by a liquid container 33 which extendsupwardly at both sides of the box above the ends of the contact faces31. The suction box 343 is also shown as provided with a connection. 35at its upper end adapted to be connected to a suction pump as describedhereinafter,

and the downspout of the suction box is indicated at 36.

In operation with this filter as shown, each cell begins to fill withliquid as it passes below the level of the liquid in the vat. When agiven cell and its associated discharge duct reach the positionindicated in Fig. 3, the duct is substantially filled with liquid, andthere is also The discharge end of each duct is some-liquid in the"cell. but also still some air. In the position of Fig. 3, the ductoutlet 26 is shut off by the entering side of'the'contact face 31, butas the drum 1'0 tates from this position, the duct outlet registers withthe suction area of the suction box as indicated. in Fig. .2, in-

which position the full effective suction of the suction box will beapplied to the duct to draw-out theliquid whichhas collected therein.

After each duct outlet 26 has passed the suction area of the suctionbox, it engages and is closed by the leaving side of the contact face 31as shown in Fig. 2. However, since the suction applied tothe duct by thesuction box has substantially emptied it of liquid, a partial vacuumhasbeen created therein, and as the duct outlet moves across the contact.face 31, thispartial vacuum.-creates new eifective suctionthrough.theperforateoutcr surface ofthe associated cell20.Thenwhentheduct outlet passes beyond the contact face 31 as indicated inFig. 4, it isagain. opened to permit it to drain into theliquid chamber33 surrounding the suction box. Preferred results are obtained if thecontact face 31 is so proportioned that the duct outlet is shut off atapproximately the same moment when the face of its corresponding cellemerges from the liquid within the vat, and it is also desirable tomaintain sufiicient height of liquid in container 33 to submerge allparts of contact face 31 at all times.

It will accordingly be seen that this construction of filter providesfor highly effective and efficient operation. There are no less thanthree distinct suction periods during each revolution of a given cell,namely, the first interval beginning when the cell passes below theliquid level and continuing until the discharge end of its duct is firstclosed by its contact face 31, the second interval when suction isdirectly applied to the duct of the suction box, and the third intervalwhen the partial vacuum is effective within the cell as the dischargeend of its duct passes from the suction box across the contact face 31.Another advantage of this filter is the reduced power requirements forits operation, resulting from the fact that the cells and ducts containrelatively little liquid while they are on the rising side of the drum.

As pointed out above, the filter of the invention is especially adaptedfor the filtering and washing of pulp to obtain concentrated liquortherefrom, and Figs. 2 and 3 illustrate operation of the filter for thispurpose. The liquid discharged into the chamber 33 is shown as flowingover a darn 49 into an outer chamber 41 from which a pipe 42 leads to apump 44 arranged to pump this liquid to the first set of shower pipes45above the liquid level in the vat. Thusv this filtered liquid is sprayedback throughthe .pulp for primary washing and is again recovered throughthe filter. be-supplied to the second stage'of shower pipes 46 asindicated in Fig. 2.

Fig. 1 also illustrates the operation of the invention with the liquidrecovered in chamber 33 being supplied to the downspout 36 of thesuction box 30 to increase the effective suction therein. A pipe 50connects the chamber 41 with the downspout 36, and the upper end of thispipe within the chamber .41 iscontrolled by a valve 51 operated by afloat 52 in chamber 41. Thus when the liquid in the chamber 41 reaches apredetermined level, the. valve 51 will open to supply this liquiddirectly to the downspout 36. It will also be apparent as previouslynoted that if there is foam or gas with the liquid entering the suctionbox, it is readily removed by way of the connection 35 and any suitablesuction pump 55 as indicated in Fig. 2.

Figs. 5-7 show another construction of filter in accordance with thepresent invention in which the discharge ducts discharge axially at oneend of the drum, and the suctionbox is correspondingly arrangedfor-contact with the end of'thedrum. In these, views, the strainer 60.issupported by a drum casing. 61 'having'end plates 62 and 6.3:mounted onshaft 64. The spaceibetween'thestrainer? If desired, clean water can.

and'casing'61 is divided into cells 65 by walls 66 'which extendforwardly in the direction of the rotation of the drum to establish arelatively flat V-shape for the cells 65, reference being made in thisconnection to my copending application Serial No. 297,746, filed July 8,1952, and issued January 24, 1956, as Patent No. 2,732,080 to the sameassignee as this application. The discharge ducts 70 from the cells 65are formed by helically arranged partitions 71 mounted between the outersurface of the casing 61 and a cylindrical cover 72 of lesser diameterthan the strainer 60 to leave a space 73 therebetween' which is closedat its outer end by a ring- 74 between'the strainer 60 and cover 62.

Asshown inFig; 7, each partition 71 leads .fromthe point formed by oneof the V-shaped walls 66 to the end of the drum, and since these walls66 lie only in the spaces radially outwardly of cover 72 and axially tothe right of this cover in Fig. 5, this leaves an outlet opening 75 foreach cell into itsassociated duct. The liquid entering each cell throughthe strainer thus flows from both ends of the drum to the outlet opening75 as indicated by the arrows-in Fig. 7, and the discharge ends of theducts are indicated at 77 in Fig.7. The suction box 80 is accordinglymounted outside this end of the drum, and it includes a verticallyarranged extended contact face 81 of generally crescent shape forclosing engagement with the discharge openings 77 in the same manner asalready describedin connection with Figs. 1-4. The liquid con tainer 83corresponds to the part 33 as described in connectionwith Figs. 1-4 andoperates in the same manner.

The invention is equally applicable to drum filters in which a pairofducts extend from each cell to opposite ends of the drum. Fig. 8 showssuch a filter construction which is generally as described in connectionwith Fig. 1

' but includes two ducts 25 leading from each outlet 22 to the oppositeends of the drum, and these ducts are arranged in opposite spirals toposition their discharge ends at the desired angular spacing rearwardlyof their associated cell and outlet. A suction box 30 is accordinglyprovided at both ends of the filter, with each functioning in the samemanneras described in connection with Figs. 1-4.

While the forms of apparatus herein described constitute preferredembodiments of the invention, it is to be understood that the inventionis not limited to these precise forms of apparatus, and that changes maybe made therein without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:

1. A rotary suction drum filter comprising a drum casing, a cylindricalstrainer disposed in concentric outwardly spaced relation to theoutersurface of said casing, generally radially arranged walls disposedbetween said casing and said strainer to define a plurality of cells inthe space between said strainer and said casing-means ends of successivesaid ducts during a minor fraction'of a complete revolution of each saidduct'to withdraw collected liquid therefrom with resulting creation of apartial vacuum. therein, means cooperating with said suction box toclose the discharge end of each said duct for a further minor fractionof a complete revolution to provide for suction through said strainerinto the associated said cell under the influence of said vacuumtherein, and conduit means positioned for registry with said dis-'charge ends of successive said conduits following said further minorfraction'of a complete revolution to receive therefrom the liquidaccumulated therein during said further minor fraction of a revolution.

2. A rotary suction drum filter comprising a drum cas ing, a cylindricalstrainer disposed in concentric outwardly spaced relation to the outersurface of said casing, generally radially arranged walls disposedbetween said casing and said strainer to define a plurality of cells inthe space between said strainer and said casing, means forming aseparate discharge outlet from each of said cells, discharge ductsextending from said outlets to a discharge position at one end of saiddrum and being bent rearwardly in the direction of rotation of said drumto locate the discharge end of each of said ducts at a substantialangular distance rearwardly of the associated said outlet, a suction boxlocated at said one end of said drum and arranged for registry with saiddischarge ends of successive said ducts during a minor fraction of acomplete revolution of each said duct, and a liquid containersurrounding said suction box and adapted to register with said dischargeends of successive said duets following movement thereof past saidsuction box for receiving further discharge of liquid from said ducts.

3. A rotary suction drum filter comprising a drum casing, a cylindricalstrainer disposed in Concentric outwardly spaced relation to the outersurface of said casing, generally radially arranged walls disposedbetween said casing and said strainer to define a plurality of cells inthe space between said strainer and said casing, means forming aseparate discharge outlet from each of said cells, discharge ductsextending from said outlets to a discharge position at one end of saiddrum and being bent rearwardly in the direction of rotation of said drumto locate the discharge end of each of said ductsat a substantialangular distance rearwardly of the associated said outlets, a suctionbox located at said one end of said drum and arranged for registry withsaid discharge ends of successive said ducts during a minor fraction ofa complete revolution of each said duct to withdraw collected liquidtherefrom with resulting creation of a partial vacuum therein, meanscooperating with said suction box to close the discharge end of eachsaid duct for a further minor fraction of a complete revolution toprovide for suction through said strainer into the associated said cellunder the influence of said vacuum therein, and a liquid containersurrounding said suction box and said cooperating means for receivingthe further discharge of liquid from said ducts following movement ofthe successive discharge ends thereof past said cooperating means.

4. A rotary suction drum filter comprising a drum casing, a cylindricalstrainer disposed in concentric outwardly spaced relation to the outersurface of said casing, generally radially arranged Walls disposedbetween said casing and said strainer to define a plurality of cells inthe space between said strainer and said casing, means forming aseparate discharge outlet from each of said cells, discharge ductsextending from said outlets to a discharge position at one end of saiddrum and being bent rearwardly in the direction of rotation of said drumto locate the discharge end of each of said ducts at a substantialangular distance rearwardly of the associated said outlet, a suction boxlocated at said one end of said drum and arranged for registry With saiddischarge ends of successive said ducts during a minor fraction of acomplete revolution of each said duct, a liquid container surroundingsaid suction box and adapted to register with said discharge ends ofsuccessive said ducts following movement thereof past said suction boxfor receiving further discharge of liquid from said ducts, and means forconducting said liquid from said container to a position above said drumand for spraying said liquid onto the surface of said drum above thelevel of liquid outside said drum.

5. A rotary suction drum filter comprising a drum casing, a cylindricalstrainer disposed in concentric outwardly spaced relation to the outersurface of said casing, generally radially arranged walls disposedbetween said casing and said strainer to define a plurality of cells inthe space between said strainer and said casing, means forming aseparate discharge outlet from each of said cells, discharge ductsextending from said outlets to a discharge position at one end of saiddrum and being bent rearwardly in the direction of rotation of said drumto locate the discharge end of each of said ducts at a substantialangular distance rearwardly of the associated said outlet, a suction boxlocated at said one end of said drum and arranged for registry with saiddischarge ends of successive said ducts during a minor fraction of acomplete revolution of each said duct, a downspout leading from saidsuction box, a liquid container surrounding said suction box and adaptedto register with said discharge ends of successive said ducts followingmovement thereof past said suction box for receiving further dischargeof liquid from said ducts, and means for conducting said liquid fromsaid container to said downspout for increasing the effective suction insaid suction box.

References Cited in the tile of this patent UNITED STATES PATENTS1,359,578 Costello Nov. 23, 1920 2,111,843 Daman Mar. 22, 1938 2,139,445Dinwiddie Dec. 6, 1938 2,537,414 Lindblad Jan. 9, 1951 2,548,999 OliverApr. 17, 1951 2,588,976 Fuhrmeister Mar. 11, 1952 FOREIGN PATENTS588,818 Germany Nov. 27, 1933 865,106 Germany Jan. 29, 1953

